Crunch is an arbitrary-precision integer arithmetic library for JavaScript. It is designed to execute arithmetic operations as quickly as possible, in particular those upon which asymmetric encryption cryptosystems such as RSA are built.

InfinityTK is a light-weight application development toolkit with utilities for OpenGL window creation, OpenGL function loading, keyboard/mouse events, image loading, header only 3D mathematics, and all you would need to start creating graphical applications in C++11.

MathMod is mathematical software for visualizing and animating parametric and implicit surfaces. It is an extension/rewrite of the K3DSurf project. It supports 3D/4D plotting and animation, a scripting language, a JSON file format with a large set of scripted examples, and an OBJ output file of the 3D mesh.

wasora is a computational tool designed to aid a cognizant expert, whether an engineer, scientist, technician, or geek, to analyze complex systems by solving mathematical problems by means of a high-level plain-text input file containing algebraic expressions, data for function interpolation, differential equations, and output instructions amongst other facilities. At first glance, it may look like another high-level interpreted programming language, but it should be seen as a syntactically-sweetened way to ask a computer to perform a certain mathematical calculation. For example, the famous Lorenz system may be solved by writing the three differential equations in a human friendly plain text file.

The Graphical Models Toolkit (GMTK) is a toolkit for rapidly prototyping statistical models using dynamic graphical models (DGMs) and dynamic Bayesian networks (DBNs). It can be used for speech and language processing, bioinformatics, activity recognition, and any time series application. It features exact and approximate inference, many built-in factors including dense, sparse, and deterministic conditional probability tables, native support for ARPA backoff-based factors and factored language models, parameter sharing, gamma and beta distributions, dense and sparse Gaussian factors, heterogeneous mixtures, deep neural network factors, and time-inhomogeneous trellis factors, arbitrary order embedded Markov chains, a GUI graph viewer, and much more.

LibBi is used for state-space modelling and Bayesian inference on high-performance computer hardware, including multi-core CPUs, many-core GPUs (graphics processing units), and distributed-memory clusters.
The staple methods of LibBi are based on sequential Monte Carlo (SMC), also known as particle filtering. These methods include particle Markov chain Monte Carlo (PMCMC) and SMC2. Other methods include the extended Kalman filter and some parameter optimization routines.
LibBi consists of a C++ template library and a parser and compiler, written in Perl, for its own modelling language.

GTKMathplot is an interactive plotting program based on GTK+ and the Cairo graphics library. It can display bidimensional curves, tridimensional curves, and surfaces from Cartesian or parametric equations describing the mathematical objects you would like to visualize. It is designed to be intuitive for high school students with good mathematical knowledge. University students of engineering, physics, mathematics, or natural sciences should need no explanation at all to start using it proficiently.